Substituents on an aromatic ring can have several effects on electrophilic aroma

Question

Substituents on an aromatic ring can have several effects on electrophilic aromatic substitution reactions. Substituents can activate or deactivate the ring to substitution, donate or withdraw electrons inductively, donate or withdraw electrons through resonance, and direct substitution either to the ortho/para or to the meta positions. From the following lists, select the substituents that have the indicated property. The substituents are written as -XY, where X is the atom directly bound to the aromatic ring.. Activation of the ring towards substitution. -Br -OCOCH3 -COOH -NHCOCH3 Withdrawal of electrons through resonance. -OCH3 -SO3H -OH -NO2 Ortho/para-directed substitution. -Cl -NHCOCH3 -CN -CH3 -COOH

Explanation / Answer

Activation of the ring towards substitution- correct answer is NHCOOCH3. Reason: All groups (except halo groups) having electron lone pair of electron on the atom directly attached to the aromatic ring activates the ring towards electrophilic aromatic substitution. Withdrawal of electrons through resonance-correct answer is SO3H, NO2. Reason: All groups in which electronegative atoms having pie bond and is directly attached to the aromatic ring withdraws electron through resonance. Ortho/para-directed substitution- correct answer is Cl, NHCOCH3, CH3 Reason: All groups having electron lone pair of electron on the atom directly attached to the aromatic ring. Exception to this rule are alkyl group in this case there is no lone pair of electron but they are ortho/para directing group.

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